geom_slab {ggdist}

Slab (ridge) plot (shortcut geom)

Description

Shortcut version of geom_slabinterval() for creating slab (ridge) plots.

Roughly equivalent to:

geom_slabinterval(
  show_point = FALSE,
  show_interval = FALSE
)

Usage

geom_slab(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  orientation = NA,
  normalize = "all",
  fill_type = "segments",
  subguide = "none",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

mapping

Set of aesthetic mappings created by aes(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).

stat

The statistical transformation to use on the data for this layer, either as a ggproto Geom subclass or as a string naming the stat stripped of the stat_ prefix (e.g. "count" rather than "stat_count")

position

Position adjustment, either as a string, or the result of a call to a position adjustment function. Setting this equal to "dodge" (position_dodge()) or "dodgejust" (position_dodgejust()) can be useful if you have overlapping geometries.

...

Other arguments passed to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or linewidth = 3 (see Aesthetics, below). They may also be parameters to the paired geom/stat.

orientation

Whether this geom is drawn horizontally or vertically. One of:

• NA (default): automatically detect the orientation based on how the aesthetics are assigned. Automatic detection works most of the time.

• "horizontal" (or "y"): draw horizontally, using the y aesthetic to identify different groups. For each group, uses the x, xmin, xmax, and thickness aesthetics to draw points, intervals, and slabs.

• "vertical" (or "x"): draw vertically, using the x aesthetic to identify different groups. For each group, uses the y, ymin, ymax, and thickness aesthetics to draw points, intervals, and slabs.

For compatibility with the base ggplot naming scheme for orientation, "x" can be used as an alias for "vertical" and "y" as an alias for "horizontal" (ggdist had an orientation parameter before base ggplot did, hence the discrepancy).

normalize

How to normalize heights of functions input to the thickness aesthetic. One of:

• "all": normalize so that the maximum height across all data is 1.

• "panels": normalize within panels so that the maximum height in each panel is 1.

• "xy": normalize within the x/y axis opposite the orientation of this geom so that the maximum height at each value of the opposite axis is 1.

• "groups": normalize within values of the opposite axis and within each group so that the maximum height in each group is 1.

• "none": values are taken as is with no normalization (this should probably only be used with functions whose values are in [0,1], such as CDFs).

For a comprehensive discussion and examples of slab scaling and normalization, see the thickness scale article.

fill_type

What type of fill to use when the fill color or alpha varies within a slab. One of:

• "segments": breaks up the slab geometry into segments for each unique combination of fill color and alpha value. This approach is supported by all graphics devices and works well for sharp cutoff values, but can give ugly results if a large number of unique fill colors are being used (as in gradients, like in stat_gradientinterval()).

• "gradient": a grid::linearGradient() is used to create a smooth gradient fill. This works well for large numbers of unique fill colors, but requires R >= 4.1 and is not yet supported on all graphics devices. As of this writing, the png() graphics device with type = "cairo", the svg() device, the pdf() device, and the ragg::agg_png() devices are known to support this option. On R < 4.1, this option will fall back to fill_type = "segments" with a message.

• "auto": attempts to use fill_type = "gradient" if support for it can be auto-detected. On R >= 4.2, support for gradients can be auto-detected on some graphics devices; if support is not detected, this option will fall back to fill_type = "segments" (in case of a false negative, fill_type = "gradient" can be set explicitly). On R < 4.2, support for gradients cannot be auto-detected, so this will always fall back to fill_type = "segments", in which case you can set fill_type = "gradient" explicitly if you are using a graphics device that support gradients.

subguide

Sub-guide used to annotate the thickness scale. One of:

• A function that takes a scale argument giving a ggplot2::Scale object and an orientation argument giving the orientation of the geometry and then returns a grid::grob that will draw the axis annotation, such as subguide_axis() (to draw a traditional axis) or subguide_none() (to draw no annotation). See subguide_axis() for a list of possibilities and examples.

• A string giving the name of such a function when prefixed with "subguide"; e.g. "axis" or "none".

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().

Value

A ggplot2::Geom representing a slab (ridge) geometry which can be added to a ggplot() object.

Aesthetics

The slab+interval stats and geoms have a wide variety of aesthetics that control the appearance of their three sub-geometries: the slab, the point, and the interval.

Positional aesthetics

• x: x position of the geometry

• y: y position of the geometry

Slab-specific aesthetics

• thickness: The thickness of the slab at each x value (if orientation = "horizontal") or y value (if orientation = "vertical") of the slab.

• side: Which side to place the slab on. "topright", "top", and "right" are synonyms which cause the slab to be drawn on the top or the right depending on if orientation is "horizontal" or "vertical". "bottomleft", "bottom", and "left" are synonyms which cause the slab to be drawn on the bottom or the left depending on if orientation is "horizontal" or "vertical". "topleft" causes the slab to be drawn on the top or the left, and "bottomright" causes the slab to be drawn on the bottom or the right. "both" draws the slab mirrored on both sides (as in a violin plot).

• scale: What proportion of the region allocated to this geom to use to draw the slab. If scale = 1, slabs that use the maximum range will just touch each other. Default is 0.9 to leave some space between adjacent slabs. For a comprehensive discussion and examples of slab scaling and normalization, see the thickness scale article.

• justification: Justification of the interval relative to the slab, where 0 indicates bottom/left justification and 1 indicates top/right justification (depending on orientation). If justification is NULL (the default), then it is set automatically based on the value of side: when side is "top"/"right" justification is set to 0, when side is "bottom"/"left" justification is set to 1, and when side is "both" justification is set to 0.5.

Color aesthetics

• colour: (or color) The color of the interval and point sub-geometries. Use the slab_color, interval_color, or point_color aesthetics (below) to set sub-geometry colors separately.

• fill: The fill color of the slab and point sub-geometries. Use the slab_fill or point_fill aesthetics (below) to set sub-geometry colors separately.

• alpha: The opacity of the slab, interval, and point sub-geometries. Use the slab_alpha, interval_alpha, or point_alpha aesthetics (below) to set sub-geometry colors separately.

• colour_ramp: (or color_ramp) A secondary scale that modifies the color scale to "ramp" to another color. See scale_colour_ramp() for examples.

• fill_ramp: A secondary scale that modifies the fill scale to "ramp" to another color. See scale_fill_ramp() for examples.

Line aesthetics

• linewidth: Width of the line used to draw the interval (except with geom_slab(): then it is the width of the slab). With composite geometries including an interval and slab, use slab_linewidth to set the line width of the slab (see below). For interval, raw linewidth values are transformed according to the interval_size_domain and interval_size_range parameters of the geom (see above).

• size: Determines the size of the point. If linewidth is not provided, size will also determines the width of the line used to draw the interval (this allows line width and point size to be modified together by setting only size and not linewidth). Raw size values are transformed according to the interval_size_domain, interval_size_range, and fatten_point parameters of the geom (see above). Use the point_size aesthetic (below) to set sub-geometry size directly without applying the effects of interval_size_domain, interval_size_range, and fatten_point.

• stroke: Width of the outline around the point sub-geometry.

• linetype: Type of line (e.g., "solid", "dashed", etc) used to draw the interval and the outline of the slab (if it is visible). Use the slab_linetype or interval_linetype aesthetics (below) to set sub-geometry line types separately.

Slab-specific color and line override aesthetics

• slab_fill: Override for fill: the fill color of the slab.

• slab_colour: (or slab_color) Override for colour/color: the outline color of the slab.

• slab_alpha: Override for alpha: the opacity of the slab.

• slab_linewidth: Override for linwidth: the width of the outline of the slab.

• slab_linetype: Override for linetype: the line type of the outline of the slab.

Deprecated aesthetics

• slab_size: Use slab_linewidth.

Other aesthetics (these work as in standard geoms)

• width

• height

• group

See examples of some of these aesthetics in action in vignette("slabinterval"). Learn more about the sub-geom override aesthetics (like interval_color) in the scales documentation. Learn more about basic ggplot aesthetics in vignette("ggplot2-specs").

See Also

See stat_slab() for the stat version, intended for use on sample data or analytical distributions. See geom_slabinterval() for the geometry this shortcut is based on.

Other slabinterval geoms: geom_interval(), geom_pointinterval(), geom_spike()

Examples

library(dplyr)
library(ggplot2)

theme_set(theme_ggdist())

# we will manually demonstrate plotting a density with geom_slab(),
# though generally speaking this is easier to do using stat_slab(), which
# will determine sensible limits automatically and correctly adjust
# densities when using scale transformations
df = expand.grid(
    mean = 1:3,
    input = seq(-2, 6, length.out = 100)
  ) %>%
  mutate(
    group = letters[4 - mean],
    density = dnorm(input, mean, 1)
  )

# orientation is detected automatically based on
# use of x or y
df %>%
  ggplot(aes(y = group, x = input, thickness = density)) +
  geom_slab()

df %>%
  ggplot(aes(x = group, y = input, thickness = density)) +
  geom_slab()

# RIDGE PLOTS
# "ridge" plots can be created by increasing the slab height and
# setting the slab color
df %>%
  ggplot(aes(y = group, x = input, thickness = density)) +
  geom_slab(height = 2, color = "black")